A stator vane having endwalls each with a number of rows of film diffusion slots that open onto the hot surface of each endwall. Each diffusion slot is formed with one or more separated diffusion slots each having a serpentine flow channel and one or more metering inlet holes to supply cooling air to the diffusion slot. The inlet metering holes are connected to the impingement chambers formed over the endwalls so that the spent impingement cooling air from the impingement chamber is supplied to the inlet metering holes of the diffusion slots. The combination of metering cooling air, impingement cooling, serpentine flow and diffusion provide for a high rate of cooling with a low flow rate of cooling air.
Each serpentine channel and diffusion slot can be formed with one or more separated serpentine channels and diffusion slots to provide for different flow and pressure requirements depending upon the external hot gas pressure and temperature profiles. Separation ribs are used within the serpentine channels and the diffusion slots to form separated slots.